1. Field of the Invention
This invention relates to a multiple disk friction clutch, and more particularly to a friction clutch which includes a countertorque limiter mechanism for preventing a countertorque from a driven shaft side from excessively rotating a driving shaft.
2. Description of Background Art
Various examples have conventionally been proposed which include a countertorque limiter mechanism which moves, when a countertorque is inputted, a pressure plate in a direction away from a clutch center member to weaken the frictional engagement of the friction clutch. Examples of this are disclosed in Japanese Patent Publication No. Hei 5-73928 and Japanese Patent Laid-Open No. Sho 59-219525.
The example disclosed in Japanese Patent Publication No. Hei 5-73928 is shown in FIG. 8.
A friction clutch 01 of FIG. 8 performs connection and disconnection between a main shaft 02 which is a driven shaft and a driving gear 03 supported coaxially for rotation on the main shaft 02.
A bottomed cylindrical clutch outer member 04 is provided integrally on the driving gear 03, and a plurality of clutch friction plates 05 are supported for sliding movement in an axial direction on an inner periphery of the clutch outer member 04. An equal plural number of clutch plates 06 disposed alternately between the clutch friction plates 05 are provided for sliding movement in an axial direction on a circumference of a clutch hub 07.
The clutch hub 07 is divided in the axial direction into two members of a main hub 08 and a sub hub 09. The main hub 08 on the inner bottom side of the bottomed cylindrical clutch outer member 04 is fitted integrally on the main shaft 02 and corresponds to a clutch center member, and a flange portion thereof is opposed to the clutch friction plates 05 and the clutch plates 06.
The sub hub 09 is fitted for sliding movement in the axial direction on an inner peripheral face of a tubular portion of the main hub 08 and is connected to the main hub 08 by way of a cam mechanism 011.
A cone spring 010 is interposed in a compressed condition between the main hub 08 and the sub hub 09.
A cam mechanism 011 is constituted from a cam pawl 012 and a pawl hole 013 and converts, by the combination of them, a relative rotational displacement between the main hub 08 and the sub hub 09 into a sliding displacement in an axial direction of the sub hub 09.
The sub hub 09 contacts, at a right end thereof, with a pressure plate 014 disposed in such a manner as to close up an opening of the clutch outer member 04, and the pressure plate 014 cooperates with the clutch center member of the main hub 08 to hold the clutch friction plates 05 and the clutch plates 06 therebetween.
A rod 015 provided projectingly on the main hub 08 extends through the pressure plate 014, and a clutch spring 016 in the form of a coil spring is interposed in a compressed condition between an end of the rod 015 and the pressure plate 014.
The pressure plate 014 is supported at the center thereof by a release bearing 017, and a release rod 018 which extends coaxially through the main shaft 02 contacts, at a right end thereof, with the release bearing 017.
The release rod 018 moves in response to operation of a clutch lever or the like.
In the friction clutch 01 of the structure described above, in an ordinary connection condition of the clutch, the pressure plate 014 urges, under the biasing force of the clutch spring 016, the clutch friction plates 05 and the clutch plates 06 toward the main hub 08 to strengthen the frictional engagement between the clutch friction plates 05 and the clutch plates 06.
When the clutch is to be disconnected, the release rod 018 is moved in the rightward direction in FIG. 8 by operation of the clutch lever to move the pressure plate 014 against the clutch spring 016 to increase the distance between the main hub 08 and the pressure plate 014 to cancel the frictionally engaging condition.
Upon acceleration or ordinary running, a torque is applied to the forward side in the direction of rotation from the sub hub 09 to the main hub 08, and the cam mechanism 011 positions the sub hub 09 leftwardly so that the pressure plate 014 urges, under the biasing force of the clutch spring 016, the clutch friction plates 05 and the clutch plates 06 toward the main hub 08 to maintain the frictionally engaging condition.
Upon decelerating running or until the vehicle is stopped, an engine brake operates, and a counter torque is applied to the rear side in the direction of rotation from the main hub 08 on the main shaft 02 side to the sub hub 09. The cam mechanism 011 thus moves the sub hub 09 rightwardly to move the pressure plate 014 away from the main hub 08 to weaken the frictional engagement between the clutch friction plates 05 and the clutch plates 06.
Consequently, a suitable degree of slip is produced between the clutch friction plates 05 and the clutch plates 06 to prevent excessive rotation of the engine and prevent the engine brake from operating excessively.
In this manner, in the conventional friction clutch which includes a countertorque limiter mechanism, the main hub 08 serving as a clutch center member and the pressure plate 014 rotate integrally with each other in the direction of rotation. When a countertorque is applied, the sub hub 09 is rotated relative to the main hub 08. The relative rotation is converted into a displacement in an axial direction by the cam mechanism 011 so that the sub hub 09 pushes the pressure plate 014 in the axial direction to move the pressure plate 014 away from the main hub 08 to weaken the frictional engagement.
Accordingly, an intermediate member such as the sub hub 09 which rotates, when a countertorque is applied, relative to the main hub 08 and converts the relative rotation into a displacement in an axial direction to act upon the pressure plate 014 is required, which makes the construction complicated and requires a high cost.
Since the conventional friction clutch has such a structure that it includes the pressure plate 014 on the opening side of the clutch outer member 04 and the pressure plate 014 is pushed outwardly in order to disconnect the clutch, the release mechanism has a complicated structure wherein the release rod 018 extends through the main shaft 02 and pushes out the pressure plate 014. Even where the conventional friction clutch is applied to an apparatus wherein the release mechanism is provided on the opening side of the clutch outer member 04, the construction wherein the pressure plate 014 is pulled must be employed which makes the structure complicated.